A Tadpole Shrimp is Found in Spain - Observation of the Week, 12/23/19

Our Observation of the Week is this Iberian tadpole shrimp, seen in Spain by @mario_mairal!

“I am an evolutionary biologist and naturalist,” says Mario Mairal, who is originally from Spain but is currently a researcher with Stellenbosch University in South Africa. “I am working with different topics related to biodiversity and evolution [and] I am especially focused on the biogeography of sub-Antarctic islands and African sky-islands, extinctions as drivers of biogeographical patterns, or the loss of dispersal on island hypothesis.”

Mario’s research and interests have led him on expeditions in the Canary Islands, Magascar, Northern Africa, the Galápagos Islands, and of course his home country of Spain, where he came across the tadpole shrimp you see pictured above.

“In March 2014, along with other young passionate friends of nature, we decided to make a weekend trip to visit a forestry guardian friend in a rural region of Spain (Piedrabuena, Ciudad Real),” he recalls.

My friend is an expert in the area and it was the perfect time to photograph daffodils, amphibians and Eurasian otters. When we were looking for amphibians near a pond, we found suddenly a great abundance of Triops.

Triops is one of two genera in the family Triopsidae, commonly known as “tadpole shrimp” in English. While it is a crustacean, this omnivorous creature is not a shrimp and is definitely not a tadpole, although its silhouette resembles that of larval anurans. These creatures tend to live in temporary ponds, and their eggs can tolerate long periods of dry conditions, hatching only when the pond’s water has returned.  

Mario (above, in South Africa) of course focuses on research, but also tells me, “I am especially interested in the dissemination of science. As a scientist I find that dissemination should be an obligatory task.” He released photos for free use on his website, and joined both iNaturalist and Instagram as well, “because I think that nowadays is imperative to arouse curiosity, educate in conservation and warning about the current biodiversity crisis.”

Although he only joined iNaturalist this past July, Mario says that “I have quickly learned many things which, before using iNaturalist, I would have spent hours looking up in other publications. I am impressed by the power of collective consciousness.” But he also hopes to use it for his research:

For example, I am especially interested in distribution patterns and processes that model biodiversity, and I am sure that iNaturalist is helping me to understand these patterns better. And with this information I can establish a hypothesis to unravel the evolutionary processes. Now I am studying historical distribution patterns because of climate change, and iNaturalist has deeply inspired me several times.

- by Tony Iwane. Some quotes have been lightly edited for clarity and flow.

- In addition to photography and biology, Mario is also a magician, and you can see some clips of him performing here.

- Triops longicaudatus eggs are often sold in kits for people to raise at home. This video has some nice close up footage of one swimming.

Posted by tiwane tiwane, December 23, 2019 22:12



"evidence shows they have not evolved significantly in over 250 million years"
That is false. There's no such thing as a lineage that barely changes in 250 million years. The "living fossil" narrative needs to die in a fire. It's based on subjectivity and ignorance. And it's not just a pedantic argument---it's resulted in some clades going un- or understudied for far too long because people just assumed little to no change was present without actually looking into it.

But I don't want to leave a purely critical comment because of one sentence and a title. Tadpole shrimp are quite cool! Thanks for highlighting them. And his work sounds really interesting.

Posted by jessm-c about 1 month ago (Flag)

@jessm-c I'm quite ignorant, being just an undergraduate student, but don't some groups of animals evolve at a slower rate than others? I know some species reproduce purely by parthenogenesis, for example. And looking at genetic data shows variation in how much genetic divergence has taken place over time between groups. Branchiopods can be restricted to very specific niche habitats and they are closed off from other populations. Maybe, relatively speaking, a sound argument could be made that they haven't changed much? I guess it all depends on what we might mean by 'significant'. They sure seem morphologically similar (especially considering how other groups have changed after 250 million years). But, again, I'm pretty clueless haha.

I really love triops and fairy shrimp. I got sea monkeys as a child and I've been in love with the branchiopods ever since. So cool.

Posted by kruma about 1 month ago (Flag)

Thanks for the comment and link, @jessm-c. I'm certainly not tied to the term "living fossil," and as someone who's done snake and spider outreach, certain inelegant and inaccurate terms and concepts commonly applied to those animals frustrate me, so I hear you. Made some slight edits.

And yes, tadpole shrimp are amazing! I remember seeing my first ones in 2010 (the same ones @kueda documented here) and my mind was blown.

Posted by tiwane about 1 month ago (Flag)

I am quite surprised with its common name in English: “tadpole shrimp”!

In Russian it is called "Щитень", and that is surprisingly original name. Although a specific term, it definitely has a "shield" root(so it is like shield-bearer, or shield-like). Honestly, I was expecting the same root(shield) in other languages, but this is definitely not the case. Both "tadpool shrimp" in English, "Urzeitkrebse"(=ancient crab) in German, and "Щитень" in Russian are original and have nothing in common. That likely means, that people in many countries do know them for quite a long time and name them independently...

*and that is definitely a reason, why scientist love Latin names.)

Posted by krokozavr about 1 month ago (Flag)

Thanks, @tiwane! And thank you for putting the term in quotes in the first place, too.

Posted by jessm-c about 1 month ago (Flag)

@kruma You're right, speed is certainly a thing that varies between groups. But even slow is not stasis, and 250 million years is a very long time, so even slowly-changing lineages will accumulate a lot of change. Tuatara are another thing that get called "living fossils" because they're the only species left out of a once-diverse lineage. But they're actually evolving *extremely* quickly genetically. Higher than any other vertebrate that's been measured in fact!

It's perfect that you bring up brachiopods, because we actually have soft tissue preservation of some very ancient ones. Even though some groups (like Lingulata) have similar-looking shells due to functional constraints, brachiopod soft tissue has undergone some extensive changes.

The part you bring up about what is significant and what is not is where the subjectivity comes in. How much change is "enough"? Why is one trait or measure more important than another? Who decides? How to get other researchers to stop using it when someone who studies the group they're ascribing it to stands up and says "no?" How many groups will be left after that? Genetic rate, matrices of morphological traits, number of species left relative to some measure of previous diversity... Reasons things get called "living fossils" aren't even multi-modal when you start sampling things, just a complete smear, so the term is scientifically meaningless.
As for ignorance, give me something that's been called a "living fossil", and if there's a fossil record, the supposed lack of change can be directly disproved. There's a reason the term gets used more often by neontologists than by paleontologists. Y'all know more about things like behavior, genetics, and soft tissue, we know more about things like the sampled history of lineages and their morphological evolution. A lot of us who study the extinct species rail against the term because it's being used to describe a supposed lack of changes, or changes that have arbitrarily been called insignificant by people who simply haven't looked at the changes many of us have devoted our careers to describing. Though it's a bit odd when you consider that genetic changes will accumulate no matter what, so when a neontologist uses the term, it's like they're ignoring a fundamental aspect of their own field...

Another thing that's important to point out is the phylogenetic distribution of what gets called a "living fossil" and what doesn't. Sharks and their relatives are "living fossils" because they've been around for almost 450 million years, but guess what else has been around that long? Their sister clade, the bony fish, which don't, as a group, get called "living fossils". Guess which one we're a part of? There are two species of coelocanth alive---"living fossil". But there's only one species of human left---not a "living fossil". Monotremes still lay eggs---"living fossil". But therians like us haven't evolved electroreception---unimportant, not "living fossils". So there's an anthropocentric bent to it. The closer to us a clade is, the less likely it gets called a "living fossil". ...And it gets worse.
"Primitive" is a term that's inextricably tied to "living fossils". It's the one used to describe the traits themselves that supposedly remain static in "living fossils". Guess what kind of humans have historically been called "primitive", even "living fossils"? Hint: It's not the ones who left the hunter-gatherer lifestyle behind and went through an Industrial Revolution. Not the ones who've been in charge of the Western scientific tradition for much of its history. Not the ones whose skin underwent a drastic change in tone halfway through the Holocene, separate evolutions of it excepted (see where I'm going?). If you read older scientific and science-adjacent literature discussing humans, it's everywhere. Which means the "'living fossils' are things that do not look like me" trend has an unbroken extension to intraspecies prejudice, not just interspecies.

And like I said, its use has stymied research. A well-respected scientist named William Buckland said my group (Crocodyliformes) hadn't changed, so don't bother studying them. For 150 years, everyone listened. There are short blurbs of "hey, I found a new fossil, here's a picture", and that's it. 40 years of actually looking into it later, and we're one of the major groups of researchers at the annual vert paleo meeting. There's always a croc session, just like there's always a dino session. The number of us and the questions we look at have expanded amazingly because there's such an insane amount to learn about crocodyliform evolution. Imagine where we'd be if the field hadn't been held back for so long by one person's voiced assumption!

Given all of that, there's really no good reason to use the term, but many reasons not to.

Posted by jessm-c about 1 month ago (Flag)

Why is the Iberian animal 'from Mauritania'?

Posted by dianastuder about 1 month ago (Flag)

There is no agreement today about what evolution is. Any species immitigably accumulate genetical changes with time. Only a few of these changes could lead to new useful mutations that are the measure of evolution in a strict sense. However, a more common but confusing understanding of evolution is the accumulation of any change or even simple divergence caused by implementation of "dormant" genes.

The tadpoles shrimps are "living" fossils only in the first, strict understanding of species evolution. Indeed, there is no evidence of new features developed from the first known fossils of Notostraca. One can speculate that by choosing to avoid fishes that tadpoles shrimps went out from the evolutionary race.

Genetic studies (Vanschoenwinkel 2012) show that all modern tadpoles shrimps come from one population living up to 55.6 mya. It could survivals from the dinosaurs' extinction. And by the way, it means that all modern tadpoles shrimps (not only Triops canceroformis) are equally kin of the 250 mya old fossils. Features that appeared in modern Notostracas have been found in >65 mya old fossils that means that they reused the old genetic arsenal to adapt to the diverse environment.

When one observes them in an aquarium, their appearance, and behavior, one can jump in mind to the world when they were the only lords... Seems no scientists studied their behavior until now; only phylogeny and sexual patterns. In many regions, you can pick up some soil from a dried pool, bring home and grow your own shrimps in a couple of days (following numerous tips from the internet).

Posted by iliafes about 1 month ago (Flag)

@dianastuder the species is found in Spain, Portugal, Italy, and northwestern Africa.

Posted by bobby23 about 1 month ago (Flag)

@iliafes Heads up, I study evolution.

Evolution is descent with modification. Period. It does not matter if that modification is a complete change of bauplan or a few nucleotides in a dead gene being switched out for others. I'm not sure why you think there isn't agreement on it. It's not confusing, nor is it subjective like the much more restrictive and arbitrary definition you're using, which I have never heard any evolutionary scientist use (particularly not ones who work with extinct animals and on the scale of geologic time).

The tadpole shrimp papers you and I linked both directly contradict your claim that no "meaningful" evolution has occurred (there's that subjectivity thing). A separation of lineages is evolution, regardless of whether you, a physicist, or me, a vertebrate paleontologist, can pick out morphological changes in a group neither of us study through a cursory glance.

When you say "there's no evidence of new features developed from the first known fossils", you're making the same mistake Buckland and everyone who listened to him made with crocs. Have you made or read a detailed comparison between the modern species and extinct ones and found them to be absolutely, unquestionably 100% identical? Or even simpler, just compared the modern species to one another. It didn't take much digging for me to find two points of difference between the extant genera (body size and shape of caudal projection). I wonder else a notostracan researcher might see? Those differences are things that evolved post-Ur-notostracan.
Here's a paper on the oldest currently known one (as of its writing, at least). It points out some features that differ between then and now. For example, that extant species are peramorphic relative to the early ones. Which in and of itself tells us some important information about how their growth strategy has *evolved* to deal with their ephemeral environments.

The 2013 paper I linked puts the split between the two extant genera well before the K/Pg boundary, so the timing of the initial (much less subsequent) radiation crown notostracans have undergone isn't certain yet. Dinosaurs didn't go extinct; there are ~10,000 species of them flying, running, and swimming today. Every single species alive today is part of a group that survived the K–Pg extinction. Pick any group of species that radiated post-250 Ma and they're all going to be equally related to their cousins from 250 Ma. Features found in humans today have been found in >65 million year old fossils. None of these things differ between clades that get called "living fossils" and clades that don't. Only a human deciding things matters for one group but not another because reasons.

Posted by jessm-c about 1 month ago (Flag)

@kruma I just noticed you said branchiopod, not brachiopod. Sorry! I'm so used to brachiopods in my day-to-day dealings and seeing Lingula in particular come up in these arguments that I completely missed seeing the 'n'.

Posted by jessm-c about 1 month ago (Flag)

@jessm-c No worries! The branchiopod vs brachiopod mix-up is a real classic. I'm sure we've all done it at least once haha. I appreciate the insight from the different opinions presented here. Thanks for the in-depth response!

Posted by kruma about 1 month ago (Flag)

@jessm-c Are you sure that you study evolution not descent with modifications:)

Confusing is that in nowadays biology the term evolution substitutes the precise Darwin's term "descent with modifications" while all other humankind understands evolution as development of complexity or hidden potential, or as physicists would say the process of "decreasing of entropy".

It places many biologists in the same row with creationists that each in their own way denies evolution.

Merry Christmas:))

Posted by iliafes about 1 month ago (Flag)

Ah, I see. It wasn't an innocent mistake. You actually are one of those people who think you know someone else's completely different field better than them. And justified with an incorrect comparison to a different principle in your own field to boot! I wouldn't presume to lecture you about physics. But sure. Your passive aggressive sign-off, smiley faces, and insults beat all the direct examples I've provided and well thought-out arguments I've made (which you've soundly ignored). There's no point in engaging any further with you.

For everyone else reading, evolution is not a ladder and has nothing to do with increasing complexity. That outdated line of thinking was common in the early days of natural history when science and religion were entwined, and thus humans were seen as the pinnacle of creation. Adaptation (and therefore evolution) is the process of things changing to be more fit to whatever their current environment is. It can result in increased complexity (e.g., from a simple lens to the eyeballs we have now), being neither less nor more complex (e.g., snouts lengthening or shortening in various crocodyliform lineages), or decreased complexity (e.g., parasites, commensals, and symbiotes that lose or simplify some traits and systems since they no longer need to rely solely on themselves for support; vestigial organs that lose at least some of their function or go away entirely when they're no longer needed (e.g., mitochondria, who have many dead genes because they no longer needed them and genetic drift eventually made them nonfunctional; our very small Cranial Nerve 0, which is 0 instead of 1 because it either wasn't noticed or acknowledged in humans by early human-focused anatomists). There are even cases of simplicity itself being the evolutionarily fit thing—like the genomes of flighted birds and bats shrinking to weigh them down less.

Again to everyone else, I'm unsubscribing from this thread because I have no desire to argue with someone who ignores and dismisses my arguments and me. If you have questions or want to engage in actual discussion, please feel free to DM me.

Posted by jessm-c about 1 month ago (Flag)

Sorry for turning the discussion off nice triops. I just wanted to say that "living fossils" is closely related to the meaning of the word "evolution". Evolution in common sense is, however, an empirical fact, otherwise, we would not be here. Who interested can find some discussions about this topic inside "evolution" books, usually British ones.
Here is sure not a place to volubly discuss it.

Posted by iliafes about 1 month ago (Flag)

Back to the real topic here: Triops!

The first ones i saw here in the Southwest U.S. were in a small cattle pond and when I stuck my dip net into the muddy water and lifted them out I was expecting to see spadefoot toad tadpoles, which I was already familiar with. The creatures wriggling around in the net were something totally alien to me and I wasn't sure what I was looking at. That was 40 years ago and I've been intrigued by these animals ever since.

Very interesting to see a photo and story about them from elsewhere in the world.

Posted by jnstuart about 1 month ago (Flag)

I've not seen a Triops or tadpole shrimp before, but the first branchiopod that I spotted blew my mind as well! Just such amazing diversity among the invertebrates!

Posted by sambiology 30 days ago (Flag)

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